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This article in SSSAJ

  1. Vol. 73 No. 2, p. 434-442
     
    Received: Dec 20, 2007
    Published: Mar, 2009


    * Corresponding author(s): John.spargo@ars.usda.gov
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doi:10.2136/sssaj2007.0437

Illinois Soil Nitrogen Test for Prediction of Fertilizer Nitrogen Needs of Corn in Virginia

  1. John T. Spargo *a,
  2. Marcus M. Alleyb,
  3. Wade E. Thomasonb and
  4. Steven M. Nagleb
  1. a Sustainable Agricultural Systems Lab., Animal and Natural Resources Inst., Bldg. 001, Rm. 201, BARC-West, 10300 Baltimore Ave., Beltsville, MD 20705
    b Dep. of Crop and Soil Environmental Sciences, Smyth Hall, Virginia Tech, Blacksburg, VA 24061

Abstract

Current N needs for corn (Zea mays L.) in Virginia are estimated based on expected yield and are adjusted to account for the estimated amounts of N mineralized from organic sources such as manures, biosolids, and legumes. The dynamic nature of soil N creates significant uncertainty in estimates of N availability from these sources. Accurate quantification of organic N mineralization during the corn growing season should improve the precision of fertilizer N recommendations. The Illinois soil N test (ISNT) has shown promise as a tool for estimating mineralizable soil N and predicting corn fertilizer N needs. Other research has found the ISNT to be poorly related to labile soil N and unrelated to corn response to fertilizer N. The objective of this study was to determine if the ISNT predicts the fertilizer N response of corn grown in a diverse set of Virginia agroecosystems. We conducted 29 on-farm fertilizer N response trials in major corn-producing regions of Virginia. The ISNT was significantly related to estimated yield without fertilizer N (R 2 = 0.57, P < 0.0001) and relative yield (R 2 = 0.64, P < 0.0001). We also found that the ISNT extracted a consistent percentage of total soil N (16.3 ± 0.7%), suggesting that it is a poor indicator of labile N. In fact, total soil N did as well as the ISNT at predicting yield without fertilizer N (R 2 = 0.53, P = 0.0002) and relative yield (R 2 = 0.64, P < 0.0001). The ISNT offered no more information about corn yield response to fertilizer N than did total soil N content.

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